The objective of this proposal is to conduct broad studies of clinical effects of antineoplastic chemotherapeutic agents in children who have malignant diseases. These investigations will be performed according to the dictates of Phase I, II, III and ancillary protocols constructed by committees of the Southwest Oncology Group. Mechanisms of actions and toxicities will be studied as will clinical and laboratory manifestations of drug effect on gross and microscopic disease. By a recent constitutional amendment, a Pediatric Division was formed. Amongst the objectives of this new division that this institution plans to vigorously support is better coordination amongst pediatricians, radiotherapists and pathologists in design of protocols and their interpretation. There is at the University of Virginia a Division of Cancer Studies whose aim is to bring together all individuals in the School of Medicine involved in cancer research, teaching and patient care for the common good of the patients and investigators. The investigators of this proposal have the endorsement of the Division.